Plunger cavity pressure control for a hydraulically-actuated fuel injector
AssigneeCaterpillar Inc.
InventorsTan Dongming, Thomas R. McClure, Scott R. Schuricht, Wang Yongxin
Life of this patent
Estimating the term…
Abstract
A fuel injector in an engine includes a spring cavity, a piston, a plunger, a spring, a fuel cavity, and a stop plate. The piston is hydraulically controlled to force the plunger down to compress fuel in the fuel cavity. However, under certain conditions, the plunger can contact the stop plate and/or the spring can become overcompressed. Both of these conditions can cause damage to the fuel injector. The present invention locates a pressure equalization channel in such a way as to dampen the motion of the piston to prevent this damage to the fuel injector.
Claims16
A hydraulically-actuated fuel injector, comprising:
- a piston body defining a piston axis;
- a spring cavity located inside the piston body and having a first cavity end and a second cavity end spaced apart from the first cavity end along the piston axis;
- a piston located substantially inside the spring cavity and moveable along the piston axis between a first position and a second position;
- and
- a pressure equalization channel disposed in the piston body and opening on one end into the second cavity, but being blocked by the piston when the piston is located between the first and second positions.
A hydraulic piston assembly, comprising:
- a piston body;
- a cavity disposed within the piston body;
- a piston disposed within the cavity and moveable between a first position and a second position, and the piston including opposing hydraulic surfaces;
- a vent hole in the piston body selectively connecting the cavity to a low pressure;
- and
- the vent hole being open to the cavity when the piston is in the first position, but the piston blocking the vent hole when in the second position.
A hydraulic damping device for a piston mechanism, comprising:
- an elongate piston body having a first end and a second end;
- a piston adapted to move reciprocally between the first and second ends, thereby defining a variable volume first chamber adjacent the first end and a variable volume second chamber adjacent the second end;
- a fluid pressurization plunger operably coupled with said piston;
- a hydraulic source adapted to supply hydraulic fluid to the piston body;
- and
- a pressure equalizing system adapted to substantially equalize pressures of the hydraulic fluid in the first and second chambers before the piston reaches the second end.
A hydraulic damping device for a piston mechanism, comprising:
- an elongate piston body having a first end and a second end;
- a piston adapted to move reciprocally between the first and second ends, thereby defining a variable volume first chamber adjacent the first end and a variable volume second chamber adjacent the second end;
- a hydraulic source adapted to supply hydraulic fluid to the piston body;
- and
- a pressure equalizing system adapted to substantially equalize pressures of the hydraulic fluid in the first and second chambers before the piston reaches the second end;
- wherein the pressure equalizing system includes a vent hole located in the piston body and fluidically connected to a low pressure.
A method of reducing overtravel of a piston, comprising the steps of:
- hydraulically moving a piston from a first position toward a second position to compress a hydraulic fluid;
- stopping the piston before reaching the second position at least in part by trapping the hydraulic fluid in a cavity;
- retracting the piston toward the first position at least in part by biasing the piston toward the first position;
- and
- the biasing step is performed by compressing a spring in the cavity.
A method of reducing overtravel of a piston comprising the steps of:
- hydraulically moving a piston from a first position toward a second position;
- stopping the piston before reaching the second position at least in part by trapping hydraulic fluid in a cavity;
- retracting the piston toward the first position at least in part by biasing the piston toward the first position;
- and
- the biasing step is performed by compressing a spring in the cavity
- wherein the stopping step is preceded by a step of closing a vent hole that opens into the cavity with the piston.
Dependencies are inferred from the claim text.